The present invention relates generally to a method and system for effecting a transformation of a video image from an original image on a TV screen applicable, for example, a system for producing a special visual effect on a television screen in a television broadcasting station.
Such a kind of special visual effect system has been proposed in which image signals in a standard television method constructed so as to form a piece of two-dimensional image having a rectangular shape are converted into digital signals. Thereafter the digital image signals are read in predetermined address locations generated within an input image memory having a memory capacity corresponding to one field. When the output image data are read out by accessing the input image memory to read out the read-in data in an order changed from the read in order according to the necessity to display the output image data on the screen of a display unit, a piece of image having a special effect such that an image derived from input image data is geometrically changed can be displayed.
In this case, a read-out address signal for the input image memory is generated by means of a read-out address transform circuit for transforming the input image address of the input image data according to the necessity.
As the read-out address transform circuit, a circuit is used in which with a three-dimensional surface data previously stored on the basis of a concept such that on the basis of input image data generating a plane image, the input image data are converted into a three-dimensional surface and a calculation to map the input image on the three-dimensional surface using the three-dimensional surface data is achieved by software calculating means.
However, there are problems in the conventional read-out address transform circuit. That is to say, a large scale of memory is not only required as a storage means for storing the three dimensional surface data but also the transform calculation for many picture elements constituting the displayed image need to be executed so that a large-sized and complicated construction of the whole special effect system cannot be avoided.
Especially, in a case when the whole screen on which the input video image is displayed is transformed into a video screen which can be viewed as if the screen were three-dimensionally inflexed, the inflexed surface being varied with time, an oversized construction of the special visual effect system exceeding a practical capacity range cannot be avoided. Therefore, it is desirable to provide a method and system for effecting a transformation of the video image which achieves a practically sufficient special visual effect described with a simple hardware construction in place of various conventional software methods.